Chassis cracked under tow pressure

Dougwe · Chief one feather

Chassis cracked under tow pressure

PeterD · Guru

Does he have air bags fitted to the rear suspension?

justcruisin01 · Guru

Talking to the guys at the local 4x4 centre a few days & they said they have been notified by the makers of air bags not to fit them to the new ford ranger & mazda bt50.

JC

Dougwe · Chief one feather

yes he does Peter and Jim

justcruisin01 · Guru

Dougwe wrote:
yes he does Peter and Jim

Did it crack where these are mounted?

Dougwe · Chief one feather

Not sure Jim, I will see him again tomorrow sometime so will ask then as he has gone up to Melbourne tonight.

justcruisin01 · Guru

Ok , just for the record my mate here has a F250, & it broke the chassis where they were fitted so not much hope for a smaller unit.

Dougwe · Chief one feather

Interesting Jim. I would have thought the air bags would take pressure away from the chassis.

wasn_me · Guru

Dougwe wrote:
Hi all,
A friend of mine has a Mazda BT 50 twin cab. He tows a CV around the 1800kg mark and the chassis of the tug has cracked.
I remember reading here somewhere about a problem with one of the ute provider's and they did a recall for memory but can't find it and think it was the BT 50, is that right.
I suggested he ring Mazda and ask before he lashes out his play money.

Is it the current model or previous model (ended 2011). I believe the current model has a 30% increase in chassis size. I have the previous model 3lt diesel, 65000 klm, 50% of that would have been towing. No problems.

Cheers Pete

Dougwe · Chief one feather

Sorry, should have said it is a 2008 model.

I have a strong feeling he is not going to be a happy camper from comments so far.

justcruisin01 · Guru

Dougwe wrote:
Interesting Jim. I would have thought the air bags would take pressure away from the chassis.

Sorry doug , they do just the opposite as they are mounted between the diff/axle housing & the chassis so right in the centre of the curved section of the chassis over the rear axle. Basicily puts the load in one spot rather than spreading it like a spring does. If used properly as in assisting the suspension in a small way then ok, but when fitted to a week suspension & expected to carry the main load then thats the end of the chassis.Speed humps are renowned for bending them due to the sharp bump.

JC.

PeterD · Guru

Dougwe wrote:
Interesting Jim. I would have thought the air bags would take pressure away from the chassis.

On the contrary, air bags compression rates increase severely in stiffness as you compress them. They become very hard when near their compressed limit. As you bump down in a rut you are imposing a very concentrated loading on a part of the chassis that is not designed to take the loading. In fact most of the loading will be transferred to that spot. Most of the load in the tub or on the tray is centred behind the centre of the axle, particularly when you have a high ball weight from the towed vehicle.

Broken backs are very common when air bags are being used. If beefed up suspension is used to compensate for heavy loads its probably because the load is carried too far back. When the agents see the tell tale signs of air bags having been used they will report this up the chain and the company will not cover this abuse of the vehicle.

glenn · Veteran Member

I was getting quote's for insurance last week I have a bt50 2011 model

ken tame was the cheapest but they stated that they would not cover it for

a bent chassis (I do not have air bags) and I believe that was through Allianz ins

PeterD · Guru

glenn wrote:
ken tame was the cheapest but they stated that they would not cover it for a bent chassis

I think any insurance company would consider a bent chassis as being self inflicted and not pay out.

GaryKelly · Guru

I was warned about getting air bags fitted so I got Ironman Plus helper springs instead (Bill12's recommendation). Glad I did. I don't tow though... I carry a slide-on. My Ford Courier is the same as the early Mazda.

bill12 · Guru

I think you will find that a lot of the failures are with xtra cab utes, as the weight is moved further aft, and it moves the pont of fulcrum, the point where the centre of effort is, is moved further back, Also.I have also seen Toyota hilux xtra cabs crack at virtually the same point. Heavier springs and towbars will help a lot.As gary said the ironman load plus overrider springs helped us. I also think the towing capacities of a lot of modern utes are overstated. If I was going to tow a large van, say 3 ton, I would think about a landcruiser or Nissan equivalent.Bt50s are STILL regarded as light 4wd utes, and should be recognized as such. Until recently, Hiluxs only had 1.5 ton (unbraked) limit.Giving a ute more power doesn't make it stronger. Bill

justcruisin01 · Guru

bill12 wrote:
I think you will find that a lot of the failures are with xtra cab utes, as the weight is moved further aft, and it moves the pont of fulcrum, the point where the centre of effort is, is moved further back, Also.I have also seen Toyota hilux xtra cabs crack at virtually the same point. Heavier springs and towbars will help a lot.As gary said the ironman load plus overrider springs helped us. I also think the towing capacities of a lot of modern utes are overstated. If I was going to tow a large van, say 3 ton, I would think about a landcruiser or Nissan equivalent.Bt50s are STILL regarded as light 4wd utes, and should be recognized as such. Until recently, Hiluxs only had 1.5 ton (unbraked) limit.Giving a ute more power doesn't make it stronger. Bill

The problem is made worse when a tub is replaced with a tray that is another half mtr longer.

Cruising Cruze · Guru

I'm glad that we listened to you now Jim

Thanks mate

Cheers John

Baz421 · Guru

REPRINTED FROM ANOTHER RECENT POST OF MINE ON ANOTHER THREAD

This week I met 2 guys with twin cab 4WD's with Firestone airbags at 90PSI,,,, primarily to keep the rig level.

I know my Firestone bags can be pumped up to that pressure but for 4WD's they say,,,,

As a general rule, the Ride-Rite Air Helper Springs will support approximately 40 lbs. of load for each p.s.i. of inflation pressure (per pair). For example, 50 P.S. I. of inflation pressure will support a load of 2000 lbs. per pair of air helper springs.

By my rough calculations this equates to 1636kg of LIFT .

SO HOW MUCH WEIGHT IS IN THE BACK TO NEED THIS and what road quality would you have??? Just curious???

I know 10psi raises my Landcruiser LC79 about 25-30mm at the rear mudflap.

I guess there will be photos of them somewhere soon.

dddp · Newbie

I wonder what sort of difference there is re the use of airbags in a coil spring vehicle where the bag is mounted in the center of the coil spring rather than airbags with leaf springs and the bag mounted above the diff/axle housing

I would assume airbags in coil springs would not load the chassis/spring mount in a position where it isn't designed to be loaded like you would get with an airbag above a leaf spring

PeterD · Guru

dddp, The use of air bags in the coil cab Patrol utes has been known to damage the upper spring mounts over the rear axles. Other makes also have had problems. Just because the bags use the same mounting points you are not totally immune from the problem.

Baz421 · Guru

PeterD wrote:
dddp, The use of air bags in the coil cab Patrol utes has been known to damage the upper spring mounts over the rear axles. Other makes also have had problems. Just because the bags use the same mounting points you are not totally immune from the problem.

Yes I upgraded rear coils on my second Pajero because of these issues. New stronger rear coils raised back about 38mm and front suspension torsion bars adjusted to suit. Worked well towing 1.2 t boat on rough dirt in the NT

Aus-Kiwi · Guru

Your really carrying too much weight and overloading vehicle big time.. Air bags are to assist !! Not to carry most the load..
By pumping them up to maintain std ride height means most the extra weight is on the bags !!!
It's not totally the fault of the air bags . More the application . A sub crossmember should be fabricated..
Or more appropriate vehicle in the first place .. An older [due to cost] Land Cruiser etc..

Aus-Kiwi · Guru

Aus-Kiwi wrote:
Your really carrying too much weight and overloading vehicle big time.. Air bags are to assist !! Not to carry most the load..
By pumping them up to maintain std ride height means most the extra weight is on the bags !!!
It's not totally the fault of the air bags . More the application . A sub crossmember should be fabricated..
Or more appropriate vehicle in the first place .. An older [due to cost] Land Cruiser etc..
I wouldn't use my 4 cyl car to tow anything but we accept this on light trucks..

Baz421 · Guru

Dougwe wrote:
Hi all,
A friend of mine has a Mazda BT 50 twin cab. He tows a CV around the 1800kg mark and the chassis of the tug has cracked.
I remember reading here somewhere about a problem with one of the ute provider's and they did a recall for memory but can't find it and think it was the BT 50, is that right.
I suggested he ring Mazda and ask before he lashes out his play money.

Hi Doug any news yet. This thread has gone very quiet. Cheers Baz